Instituto de Investigaciones Químicas, Consejo Superior de Investigaciones Cientificas (CSIC)-Universidad de Sevilla, 49 Avda Americo Vespucio, 41092 Sevilla, Spain.
J Agric Food Chem. 2010 Jul 14;58(13):8021-6. doi: 10.1021/jf1009928.
Our group has recently observed a nonlinear tendency in antioxidant capacity of different hydroxytyrosol fatty acid esters in fish oil-in-water emulsions, where a maximum of antioxidant efficiency appeared for hydroxytyrosol octanoate. These results appear to disagree with the antioxidant polar paradox. Because the physical location of the antioxidants in an oil-water interface has been postulated as an important factor in explaining this behavior, we have prepared a series of tyrosol and hydroxytyrosol fatty acid esters with different chain length and studied their surface-active properties in water, because these physicochemical parameters could be directly related to the preferential placement at the interface. We have found that tyrosol and hydroxytyrosol fatty acid esters are relevant surfactants when the right hydrophilic-lipophilic balance (HLB) is attained and, in some cases, as efficient as emulsifiers commonly used in industry, such as Brij 30 or Tween 20. Moreover, a nonlinear dependency of surfactant effectiveness is observed with the increase in chain length of the lipophilic antioxidants. This tendency seems to fit quite well with the reported antioxidant activity in emulsions, and the best antioxidant of the series (hydroxytyrosol octanoate) is also a very effective surfactant. This potential explanation of the nonlinear hypothesis will help in the rational design of antioxidants used in oil-in-water emulsions.
我们小组最近在鱼油水乳状液中观察到不同羟基酪醇脂肪酸酯抗氧化能力的非线性趋势，其中羟基酪醇辛酸酯的抗氧化效率最高。这些结果似乎与抗氧化剂极性悖论不符。因为抗氧化剂在油水界面的物理位置被认为是解释这种行为的一个重要因素，我们已经制备了一系列具有不同链长的酪醇和羟基酪醇脂肪酸酯，并研究了它们在水中的表面活性性质，因为这些物理化学参数可能与界面的优先位置直接相关。我们发现，当达到合适的亲水亲油平衡（HLB）时，酪醇和羟基酪醇脂肪酸酯是相关的表面活性剂，并且在某些情况下，它们与行业中常用的乳化剂如 Brij 30 或 Tween 20 一样有效。此外，随着亲脂性抗氧化剂链长的增加，表面活性剂的效果呈现出非线性依赖性。这种趋势似乎与乳液中报道的抗氧化活性非常吻合，而且该系列中最好的抗氧化剂（羟基酪醇辛酸酯）也是一种非常有效的表面活性剂。这种对非线性假设的潜在解释将有助于合理设计用于油包水乳状液的抗氧化剂。
